Example 7: tested! Electromagnetic compatibility tests

The "electromagnetic compatibility" of the chainflex®® -cable

The topic of "electromagnetic compatibility" is becoming increasingly important. On the one hand, this is due to an increase in electromagnetic interference fields both at long range, caused in particular by modern telecommunications and communication technology, and at close range, caused by energy technology.

On the other hand, the demands on data transmission are increasing. Signals are becoming more and more susceptible to interference and the electromagnetic environmental influences are becoming more and more diverse, with coupling between cables that are routed in parallel over a certain distance, as is often the case with energy chains, being particularly problematic. A power cable that is subject to interference acts as a generator of an electromagnetic interference field, which in turn acts on another cable, normally a signal cable, and causes conducted interference there.

We therefore introduced cables with fibre optic cables made of glass and plastic several years ago, which are also able to withstand the mechanical stress in e-chain®. The chainflex®cables with conventional copper conductors were also tested for electromagnetic compatibility in an extensive, application-oriented test programme.

For example, an asynchronous motor was connected to a frequency inverter via an unshielded power cable (chainflex® CF30). This frequency converter with pulse width modulation becomes a generator of new spectral components that were previously not present in the primary or secondary network. Parallel to this power cable, chainflex®-cable for digital signal transmission was run in e-chain® ®. This e-chainflex® CF12 cable, which was specially designed with electromagnetic compatibility in mind, can achieve particularly good results here. This cable has twisted-pair cores whose pairs are provided with a copper shield and an additional overall shield made of steel braiding. This effectively prevents interference over a wide frequency range.

Both capacitive and inductive coupling were analysed. Under the selected test conditions, it was found that even if the power and signal cables touch each other over a longer distance, error-free data transmission is possible if a shielded chainflex®cable is used and this shield is earthed on both sides. Furthermore, tests were carried out in accordance with existing electromagnetic compatibility standards. These standards provide a general basis for determining the operating behaviour of electrical devices that are repeatedly exposed to electrical interference. They have not been introduced specifically for cable. In particular, tests were carried out with the "burst generator". Here, fast transient disturbance variables are generated in pulse groups, which in particular simulate switching processes. Such processes occur, for example, when inductive loads are interrupted or when relay contacts bounce. The shielded chainflex®cables have also proved their worth here.